class_docstr: An abstract bridge class. A bridge defines how state is passed
  between encoder and decoder.
  
  All logic is contained in the `_create` method, which returns an
  initial state for the decoder.
  
  Args:
    encoder_outputs: A namedtuple that corresponds to the the encoder outputs.
    decoder_state_size: An integer or tuple of integers defining the
      state size of the decoder.
docstr: Implements the logic for this bridge.
  This function should be implemented by child classes.
  
  Returns:
    A tuple initial_decoder_state tensor or tuple of tensors.
docstr_tok: ["Implements","the","logic","for","this","bridge",".","This","function","should","be","implemented","by","child","classes",".","Returns",":","A","tuple","initial_decoder_state","tensor","or","tuple","of","tensors","."]
code: def _create(self):
      """Implements the logic for this bridge.
      This function should be implemented by child classes.
  
      Returns:
        A tuple initial_decoder_state tensor or tuple of tensors.
      """
      raise NotImplementedError("Must be implemented by child class")
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  import abc
  from pydoc import locate
  import six
  import numpy
  import tensorflow
  from tensorflow.python.util import nest
  from seq2seq.configurable import Configurable
label_desc: Use image node_id 3 for calling the Bridge obj's underlying member method code with example usage: obj._create() without return types